A base member used in a wet area (hereinafter, also referred to as a wet area base member) is used in an environment where water is present. Accordingly, water tends to adhere onto the surface of the wet area base member. A problem is known in which when the water adhering to the surface evaporates, water scale containing silica and calcium, which are components contained in tap water, is formed on the surface of the wet area base member. In addition, another problem is known in which stains of protein, sebum, mold, microorganisms, soap, and the like adhere or stick onto the surface of the wet area base member.
It is difficult to prevent the stains from adhering onto the surface of a wet area base member. Hence, ordinarily, the original state is restored by removing the stains on the surface by cleaning. Specifically, the stains are removed by an operation such as scrubbing of the surface of the wet area base member with a cloth or a sponge by using a detergent and tap water. A wet area base member is required to be easy to clean, i.e., is required to have a high stain release property.
Moreover, since a wet area base member is generally used for a long period, the stain release property is required to last for a long period, i.e., the wet area base member is required to have stain release durability. A wet area base member may be placed in a space with a window, and used in an environment where the wet area base member is irradiated indirectly with sunlight. Accordingly, such a wet area base member is required to exhibit stain release durability even in an environment where the wet area base member is irradiated with a trace amount of ultraviolet rays.
For the prevention of adherence of water scale or water-derived stains onto the surface of a wet area base member, the following technologies have been known. Japanese Patent Application Publication No. 2008-163362 (Patent Literature 1) describes a faucet on which a plating film is formed, wherein the plating film contains hydrophilic fine particles, and some of the hydrophilic fine particles partially protrude from the surface of the plating film. In addition, Patent Literature 1 states that since irregularities formed by the hydrophilic fine particles are present on the surface of the plating film, hydrophilicity is provided to the surface of the plating film to inhibit the adherence of water scale.
Japanese Patent Application Publication No. 2002-317298 (Patent Literature 2) states that a plating layer is formed on a surface of a base member, and the plating layer contains water-repellent particles made of a fluororesin. Patent Literature 2 states that water scale and the like become easy to remove, because the surface of the plating layer is made water-repellent.
Japanese Patent Application Publication No. 2014-202047 (Patent Literature 3) states that an amorphous carbon (DLC) layer is formed on a surface of a faucet, and the color difference due to the amorphous carbon (DLC) layer is limited to a specific range to retain the texture of the faucet.
On the other hand, prevention of adherence of rain-derived stains onto the surface of glass used outdoor has also been studied. Japanese Translation of PCT International Application Publication No. 2002-543035 (Patent Literature 4) states that an amorphous carbon (DLC) coating is provided on a soda inclusive glass substrate to reduce corrosion and stains on the glass substrate. Patent Literature 4 states that the amorphous carbon (DLC) coating includes at least one highly tetrahedral amorphous carbon (ta-C) layer, and that the highly tetrahedral amorphous carbon (ta-C) layer preferably has a high density and contains a high percentage of sp3 carbon-carbon bonds.
Japanese Patent Application Publication No. 2000-72488 (Patent Literature 5) states that when a layer containing silicon as a main component and an amorphous carbon layer are formed in this order on a glass base member, attachment of inorganic stains becomes less likely to occur, or stains become easy to remove. In addition, Patent Literature 5 states that when the amorphous carbon layer contains hydrogen at 5 to 20 atomic % relative to the total amount of carbon and hydrogen, the hardness increases, the scratch-resistance is improved, and the weather-resistance is improved.